It is known that human neoplasms produce a variety of hormone-like factors which cause hypercalcemia and/or hypercalciuria. This cytokine-induced mechanism occurs in both solid tumors and lymphoproliferative neoplasms. This project will gain a better understanding of the pathophysiology of this finding in patients with lymphoma and leukemia which results from the dysregulated overproduction of an active vitamin D metabolite. During the past year the GCRC has identified over 65 hospitalized hypercalcemic patients and has retrieved serum samples from the clinical laboratory. Ongoing sample acquisition is anticipated.